Carbonization Phenomena Dependence on Pressure between Insulation Sheets by Steeper Inverter Surge at Inverter Fed Motor

Recently, "carbonization phenomena on the insulation sheets" were newly detected as the unique precursor phenomena to the burning of the insulation of inverter-fed motors due to leakage current through the insulation system. We have previously studied the generation condition for the high dV/dt resulting in an inverter surge. In this study, we built an experimental setup based on an elemental model to simulate a steep surge voltages in the inverter and constructed the stator insulation inside the motor core to control the pressure between the insulation sheets. This paper reports the carbonization characteristics and the insulation design to prevent the carbonization caused by steep inverter surges.